US6884355B2 - Process for treating organic wastewater and apparatus for treating the organic wastewater - Google Patents
Process for treating organic wastewater and apparatus for treating the organic wastewater Download PDFInfo
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- US6884355B2 US6884355B2 US10/453,643 US45364303A US6884355B2 US 6884355 B2 US6884355 B2 US 6884355B2 US 45364303 A US45364303 A US 45364303A US 6884355 B2 US6884355 B2 US 6884355B2
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- anaerobic digestion
- ozone
- phosphorus
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- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
- C12M21/00—Bioreactors or fermenters specially adapted for specific uses
- C12M21/04—Bioreactors or fermenters specially adapted for specific uses for producing gas, e.g. biogas
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
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- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
- C12M45/00—Means for pre-treatment of biological substances
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- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
- C12M45/00—Means for pre-treatment of biological substances
- C12M45/06—Means for pre-treatment of biological substances by chemical means or hydrolysis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
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- C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C—CHEMISTRY; METALLURGY
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
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- C02F11/04—Anaerobic treatment; Production of methane by such processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/32—Nature of the water, waste water, sewage or sludge to be treated from the food or foodstuff industry, e.g. brewery waste waters
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/06—Sludge reduction, e.g. by lysis
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- C—CHEMISTRY; METALLURGY
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/02—Specific form of oxidant
- C02F2305/023—Reactive oxygen species, singlet oxygen, OH radical
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/28—Anaerobic digestion processes
- C02F3/286—Anaerobic digestion processes including two or more steps
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Definitions
- the present invention relates to a process for treating organic wastewater and an apparatus for treating the organic wastewater.
- anaerobic digestion As a process to treat a slurry of high concentration organic wastewater such as wastewater, from food manufacturing, organic sludge from sewage processing, and excrement from animate beings, anaerobic digestion is known in which methane that is reusable as an energy source is produced.
- anaerobic digestion is time-consuming and, moreover, about 50% of solid matter in influent wastewater is barely solubilized and the yield of methane is as low as about 50%.
- Japanese Unexamined Patent Publication No. 206785/1997 discloses a process wherein digested sludge is drawn out from an anaerobic digestion tank, denatured with ozone or high-voltage pulse discharge and, then, returned to the anaerobic digestion tank.
- Japanese Unexamined Patent Publication No. 179285/2001 discloses another process in which microorganisms producing lytic enzyme are employed. In this process, digested sludge is drawn out from an anaerobic digestion tank, subjected to solid-liquid separation and, then, thickened. Thereafter, the thickened digester sludge is treated with microorganisms producing lytic enzyme, treated with ozone under alkaline conditions and, then, returned to the anaerobic digestion tank.
- Sludge in the anaerobic digestion tank forms sludge flocs where microorganisms and/or organic polymer are highly congested.
- ozone treatment is directly applied to solid matter in digested sludge so ozone hardly permeates into the sludge floes and acts only on the surface of solids in the sludge.
- hardly soluble substances in the digested sludge are not sufficiently denatured, i.e. not sufficiently converted into easily soluble substances, and improvement in solubility of sludge solids and transformation into methane are not satisfactory.
- ozone treatment is only intended to improve solubility of the sludge so neither the effect of ozone treatment to elute out phosphorus in the sludge into the liquid phase, nor a process to recover phosphorus, nor an apparatus for recovering phosphorus, is suggested.
- the sludge is treated with heat to elute phosphorus out into the liquid phase.
- this heat treatment is only for eluting phosphorus out and other effects of this heat treatment, such as improvement in recovery of energy source, is not suggested. Therefore, an efficient process or apparatus, in which energy source and phosphorus resource are simultaneously recovered, is not realized.
- the object of the present invention is to provide a process and apparatus in which solubility of solids in organic wastewater, organic sludge or digested sludge is improved, transformation of organic substances into methane is enhanced, and sludge disposal is reduced.
- Another object of the present invention is to provide a process and apparatus, in which energy and resource are simultaneously recovered, where phosphorus is eluted out and recovered from solids in organic wastewater, organic sludge or digested sludge while organic substances are transformed into methane.
- the object of the present invention is to provide a process and apparatus in which solubility of sludge is efficiently improved with less energy and lower costs, the rate of energy recovery is increased, the amount of disposed sludge is reduced, and phosphorus is eluted out for recovery as a resource.
- the present invention relates to a process for treating organic wastewater by anaerobic digestion, which comprises treating organic wastewater with ozone and successively with alkali and introducing said alkali treated organic wastewater into an anaerobic digestion tank.
- the present invention relates to a process for treating organic wastewater by anaerobic digestion, which comprises treating organic wastewater with ozone in the presence of hydrogen peroxide and introducing said ozone treated organic wastewater into an anaerobic digestion tank.
- the present invention relates to an apparatus for treating organic wastewater comprising a means for treating organic wastewater with ozone, a means for treating the ozone treated organic wastewater with alkali and an anaerobic digestion tank for anaerobically digesting the alkali treated organic wastewater.
- FIG. 2 is a graph showing the effect of time on total amount of digester gas in a process of treating organic wastewater according to the present invention.
- FIG. 3 is a graph showing concentration of eluted phosphorus in a process of treating organic wastewater according to the present invention.
- FIG. 4 is a graph showing the effect of time on TS concentration in a process of treating organic wastewater according to the present invention.
- FIG. 5 is a graph showing the effect of time on total amount of digester gas in a process of treating organic wastewater according to the present invention.
- FIG. 6 is a graph showing concentration of eluted phosphorus in a process of treating organic wastewater according to the present invention.
- FIG. 7 is a graph showing the effect of time on TS concentration in a process of treating organic wastewater according to the present invention.
- FIG. 8 is a graph showing the effect of time on total amount of digester gas in a process of treating organic wastewater according to the present invention.
- FIG. 9 is a graph showing concentration of eluted phosphorus in a process of treating organic wastewater according to the present invention.
- FIG. 10 is a graph showing the effect of sludge retention time on TS reduction in a process of treating organic wastewater according to the present invention.
- FIG. 11 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 12 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 13 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 14 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 15 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 16 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 18 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 20 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 22 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 23 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 24 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 25 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 26 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 27 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 30 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 31 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 32 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 33 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 34 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 35 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 36 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 37 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 38 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 39 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 40 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 41 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 42 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 44 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 45 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 46 is a diagram showing an apparatus embodying the present invention and a process flow of treating organic wastewater according to the present invention.
- FIG. 11 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- ozonization tank 9 As shown in FIG. 11 , ozonization tank 9 , alkalization tank 12 and solid-liquid separation tank 17 are arranged between anaerobic digestion tank 1 and organic wastewater feed conduit 2 .
- Ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- Alkaline solution storage tank 13 is connected to alkalization tank 12 via alkaline solution supply conduit 14 and conduit 14 is equipped with pump 15 for supplying alkaline solution.
- Ozonization tank 9 is connected to alkalization tank 12 via drain 16 and alkalization tank 12 is connected to solid-liquid separation tank 17 via drain 18 .
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge.
- Solid-liquid separation tank 17 is also connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- Coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- Conduit 25 for recovered phosphorus is also connected to phosphorus recovery tank 24 .
- anaerobic digestion tank 1 is connected, to solid-liquid separation tank 4 via drain 3 for drawing digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits; one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the ozone injection rate is preferably 0.01 to 0.10 g-O 3 /g-SS and more preferably 0.03 to 0.07 g-O 3 /g-SS.
- the organic sludge treated with ozone is sent to alkalization tank 12 via drain 16 for ozone treated sludge.
- Pump 15 works to supply sodium hydroxide solution from alkaline solution storage tank 13 to the alkalization tank 12 via the alkaline solution supply conduit 14 and, thereby, the organic sludge is treated with alkali.
- the organic sludge may preferably be treated with alkali for 5 to 30 minutes maintaining pH within a range of 9 to 13. With a pH smaller than 9, organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases. In addition thereto, phosphorus in the sludge is hardly eluted out with a pH smaller than 9.
- the organic sludge treated with alkali is sent to solid-liquid separation tank 17 via drain 18 and separated into sludge solid component and sludge dissolved component.
- sludge solid component means solution containing many solids of the organic sludge and the term “sludge dissolved component” means a solution containing substantially no solids of the organic sludge.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms. Meanwhile, the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- calcium carbonate solution in coagulant storage tank 21 is injected into the phosphorus containing solution flowing through drain 20 by coagulant supply pump 22 via coagulant supply conduit 23 and, thereby, phosphorus in the sludge dissolved component is fixed and precipitates as calcium phosphate.
- the precipitate in phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , while the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- the digested sludge in anaerobic digestion tank 1 is discharged from drain 3 and separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- organic sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in organic sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- all the organic wastewater introduced into the anaerobic digestion tank is treated with ozone and alkali.
- part of the organic sludge may be treated with ozone and alkali, while the rest may be introduced into the anaerobic digestion tank without ozone and/or alkali treatment.
- influent organic wastewater is introduced to the ozonization tank.
- influent organic wastewater may be introduced to the anaerobic digestion tank and digested sludge drawn from the anaerobic digestion tank may be introduced to the ozonization tank.
- digested sludge drawn from the anaerobic digestion tank may be subjected to solid-liquid separation and thickened digested sludge may be introduced to the ozonization tank.
- two or more of influent organic wastewater, digested sludge and thickened digested sludge may be introduced to the ozonization tank.
- FIG. 12 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 1 shown in FIG. 11 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water arc left out and drain 18 for alkali treated sludge is connected to anaerobic digestion tank 1 in FIG. 12 .
- the apparatus of the present embodiment conforms to that of Embodiment 1 shown in FIG. 11 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the organic sludge treated with ozone is sent to alkalization tank 12 via drain 16 for ozone treated sludge.
- Pump 15 works to supply sodium hydroxide solution from alkaline solution storage tank 13 to alkalization tank 12 via alkaline solution supply conduit 14 and, thereby, the organic sludge is treated with alkali.
- the organic sludge treated with alkali is introduced into anaerobic digestion tank 1 via drain 18 for alkali treated sludge.
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is discharged from drain 3 for digested sludge.
- the digested sludge discharged from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in the anaerobic digestion tank 1 is recovered from vent 27 .
- the present embodiment is preferable when the organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- organic sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in organic sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- all the organic wastewater to the anaerobic digestion tank is treated with ozone and alkali.
- part of the organic wastewater may be treated with ozone and alkali, while the rest may be introduced into the anaerobic digestion tank without ozone and/or alkali treatment.
- Embodiment 1 Another apparatus embodying the present invention and a process of treating organic wastewater with the apparatus is described.
- influent organic wastewater is treated with ozone and successively treated with alkali.
- digested sludge drawn from the anaerobic digestion tank is treated with ozone and successively treated with alkali.
- FIG. 13 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Conduit 34 for drawing digested sludge out is connected to anaerobic digestion tank 1 and leads to ozonization tank 9 .
- Ozonization tank 9 is connected to alkalization tank 12 via drain 16 for ozone treated sludge and alkalization tank 12 is connected to solid-liquid separation tank 17 via drain 18 for alkali treated sludge.
- Ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- Alkaline solution storage tank 13 is connected to alkalization tank 12 via alkaline solution supply conduit 14 and conduit 14 is equipped with pump 15 for supplying alkaline solution.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge.
- Solid-liquid separation tank 17 is also connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- Coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- Conduit 25 for recovered phosphorus is also connected to phosphorus recovery tank 24 .
- anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for drawing digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits; one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested with microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from the drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the digested sludge inside anaerobic digestion tank 1 is drawn out from conduit 34 and sent to ozonization tank 9 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the digested sludge treated with ozone is sent to alkalization tank 12 via drain 16 for ozone treated sludge.
- Pump 15 works to supply sodium hydroxide solution from alkaline solution storage tank 13 to alkalization tank 12 via alkaline solution supply conduit 14 and, thereby, the digested sludge is treated with alkali.
- the digested sludge treated with alkali is sent to solid-liquid separation tank 17 via drain 18 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms.
- the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- calcium carbonate solution in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by coagulant supply pump 22 via coagulant supply conduit 23 and, thereby, phosphorus in the sludge dissolved component is fixed and precipitates as calcium phosphate.
- the precipitate in phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , while the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- digested sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in digested sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- FIG. 14 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 3 shown in FIG. 13 . More specifically, solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 for alkali treated sludge is connected to anaerobic digestion tank 1 in FIG. 14 . Other than those above, the apparatus of the present embodiment conforms to that of Embodiment 3 shown in FIG. 13 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested with microorganisms in anaerobic digestion tank 1 and, then, the sludge inside the anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the digested sludge inside anaerobic digestion tank 1 is drawn out from conduit 34 and sent to ozonization tank 9 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the digested sludge treated with ozone is sent to the alkalization tank 12 via the drain 16 for ozone treated sludge.
- the pump 15 works to supply sodium hydroxide solution from the alkaline solution storage tank 13 to alkalization tank 12 via alkaline solution supply conduit 14 and, thereby, the digested sludge is treated with alkali.
- the digested sludge treated with alkali is introduced into anaerobic digestion tank 1 via drain 18 and anaerobically digested by microorganisms.
- the present embodiment is preferable when the organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in digested sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- Embodiment 1 influent organic wastewater is treated with ozone and, successively, treated with alkali.
- Embodiment 3 digested sludge drawn from the anaerobic digestion tank is treated with ozone and, successively, treated with alkali.
- digested sludge drawn from the anaerobic digestion tank is thickened through solid-liquid separation and the thickened digested sludge is treated with ozone and, successively, treated with alkali.
- FIG. 15 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for drawing digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits; one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to ozonization tank 9 .
- Ozonization tank 9 is connected to alkalization tank 12 via drain 16 for ozone treated sludge and alkalization tank 12 is connected to solid-liquid separation tank 17 via drain 18 for alkali treated sludge.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via a conduit 19 for feeding treated sludge and connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water.
- Phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- Alkaline solution storage tank 13 is connected to alkalization tank 12 via alkaline solution supply conduit 14 and conduit 14 is equipped with pump 15 for supplying alkaline solution.
- Solid-liquid separation tank 17 is connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and coagulant supply conduit 23 equipped with a coagulant supply pump 22 connects coagulant storage tank 21 to the drain 20 .
- conduit 25 for recovered phosphorus is connected to phosphorus recovery tank 24 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested with microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is sent to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the thickened sludge After being introduced into ozonization tank 9 through conduit 7 , the thickened sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the thickened sludge treated with alkali is sent to solid-liquid separation tank 17 via drain 18 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms.
- the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- calcium carbonate solution in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by coagulant supply pump 22 via coagulant supply conduit 23 and, thereby, phosphorus in the sludge dissolved component is fixed and precipitates as calcium phosphate.
- the precipitate in the phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , while the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- thickened digested sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of solids in thickened sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- all the digested sludge returning to the anaerobic digestion tank is treated with ozone and alkali.
- part of the digested sludge returning to the anaerobic digestion tank may be treated with ozone and alkali, while the rest may be introduced into the anaerobic digestion tank without ozone and/or alkali treatment.
- FIG. 16 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 5 shown in FIG. 15 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 for alkali treated sludge is connected to anaerobic digestion tank 1 in FIG. 16 .
- the apparatus of the present embodiment conforms to that of Embodiment 5 shown in FIG. 15 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested with microorganisms in the anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is sent to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the thickened sludge After being introduced into ozonization tank 9 through conduit 7 , the thickened sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the thickened sludge treated with ozone is sent to alkalization tank 12 via drain 16 for ozone treated sludge.
- Pump 15 works to supply sodium hydroxide solution from alkaline solution storage tank 13 to alkalization tank 12 via alkaline solution supply conduit 14 and, thereby, the thickened sludge is treated with alkali.
- the thickened sludge treated with alkali is sent to anaerobic digestion tank 1 via drain 18 for alkali treated sludge and anaerobically digested by microorganisms.
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- thickened digested sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali and, more specifically, decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- all the digested sludge returning to the anaerobic digestion tank is treated with ozone and alkali.
- part of the digested sludge returning to the anaerobic digestion tank may be treated with ozone and alkali, while the rest may be introduced into the anaerobic digestion tank without ozone and/or alkali treatment.
- FIG. 17 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 1 shown in FIG. 11 is modified in such a way that conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to pH regulator 41 and pH regulator 41 is connected to anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the apparatus of the present embodiment conforms to that of Embodiment 1 shown in FIG. 11 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is sent to alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is sent to solid-liquid separation tank 17 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into pH regulator 41 via the conduit 19 .
- the sludge dissolved component is mixed with calcium carbonate solution from coagulant supply pump 22 to precipitate calcium phosphate.
- pH regulator 41 the pH of the mixture comprising the sludge solid component and the phosphorus removed sludge dissolved component is measured and adjusted to neutral, preferably 6 to 8, by adding hydrochloric acid. Thereafter, the pH adjusted mixture is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 1.
- organic sludge is synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in organic sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- the pH of the sludge solid component separated in the solid-liquid separation tank after alkali treatment may be high due to residue of sodium hydroxide from the alkali treatment and if such sludge solid component is introduced into the anaerobic digestion tank, the pH inside the tank may suddenly change to make operations thereof unstable.
- sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, as the sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge throughout the treatments.
- a more stable and efficient treatment of organic sludge, in which energy and resources are simultaneously recovered is achieved by the process of the present embodiment comprising preceding ozone and succeeding alkali treatments, separation into sludge solid component and sludge dissolved component, phosphorus removal from the sludge dissolved component, pH neutralization of sludge solid component and/or sludge dissolved component, and introduction to the anaerobic digestion tank.
- FIG. 18 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 7 shown in FIG. 17 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 for alkali treated sludge is connected to pH regulator 41 in FIG. 18 .
- the apparatus of the present embodiment conforms to that of Embodiment 7 shown in FIG. 17 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is introduced into pH regulator 41 via drain 18 for alkali treated sludge.
- pH regulator 41 the pH of the organic sludge treated with ozone and alkali is measured and adjusted to neutral, preferably 6 to 8, by adding hydrochloric acid.
- the pH adjusted organic sludge is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 7.
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- organic sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in organic sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- the pH of the organic sludge treated with alkali may be high due to residue of sodium hydroxide from alkali treatment and if such organic sludge is introduced into the anaerobic digestion tank, the pH inside the tank may suddenly change to make operations thereof unstable. According to the present embodiment, therefore, acid such as hydrochloric acid is added to the organic sludge after alkali treatment to make the pH substantially neutral. Since the organic sludge is introduced into the anaerobic digestion tank after pH neutralization, the pH of the tank hardly changes and stable operation of the tank becomes possible.
- Embodiment 7 influent organic wastewater is treated with ozone and successively with alkali and, then, introduced into an anaerobic digestion tank after the pH thereof is regulated.
- digested sludge drawn from an anaerobic digestion tank is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after the pH thereof is regulated.
- FIG. 19 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 3 shown in FIG. 13 is modified in such a way that conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to pH regulator 41 and pH regulator 41 is connected to anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the apparatus of the present embodiment conforms to that of Embodiment 3 shown in FIG. 13 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the digested sludge inside anaerobic digestion tank 1 is introduced into ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 17 .
- the sludge solid component is introduced into pH regulator 41 via the conduit 19 .
- the sludge dissolved component is mixed with calcium carbonate solution from coagulant supply pump 22 to precipitate calcium phosphate. This precipitate is drawn out from conduit 25 and the remaining solution without phosphorus is introduced into pH regulator 41 via conduit 26 .
- pH regulator 41 the pH of the mixture comprising the sludge solid component and the phosphorus removed sludge dissolved component is measured and adjusted to 6 to 8 by adding hydrochloric acid.
- the pH adjusted mixture is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 3.
- digested sludge drawn from an anaerobic digestion tank is synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in digested sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- a more stable and efficient treatment of organic sludge in which energy and resources are simultaneously recovered, is achieved by treating the digested sludge drawn from the anaerobic digestion tank with the process comprising preceding ozone and succeeding alkali treatments, separation into sludge solid component and sludge dissolved component, phosphorus removal from the sludge dissolved component, pH neutralization of sludge solid component and/or sludge dissolved component, and introduction to the anaerobic digestion tank.
- the sludge solid component after solid-liquid separation and the sludge dissolved component after phosphorus removal are mixed and the pH of the mixture is adjusted.
- the pH of the sludge solid component after solid-liquid separation and that of the sludge dissolved component after phosphorus removal may be independently adjusted before introduction to the anaerobic digestion tank.
- either one of the pH of the sludge solid component after solid-liquid separation or that of the sludge dissolved component after phosphorus removal may be adjusted.
- FIG. 20 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 9 shown in FIG. 19 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 for alkali treated sludge is connected to pH regulator 41 in FIG. 20 .
- the apparatus of the present embodiment conforms to that of Embodiment 9 shown in FIG. 19 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the digested sludge inside anaerobic digestion tank 1 is introduced into ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is introduced into pH regulator 41 via drain 18 for alkali treated sludge.
- pH regulator 41 the pH of the digested sludge treated with ozone and alkali is measured and adjusted to 6 to 8 by adding hydrochloric acid.
- the pH adjusted digested sludge is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 9.
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge drawn from an anaerobic digestion tank is synergistically affected by strong oxidation by ozone and decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- the pH of the digested sludge treated with alkali may be high due to residue of sodium hydroxide from alkali treatment and if such digested sludge is introduced into the anaerobic digestion tank, the pH inside the tank may suddenly change to make operations thereof unstable. According to the present embodiment, therefore, acid such as hydrochloric acid is added to the organic sludge after alkali treatment to make the pH substantially neutral. Since the organic sludge is introduced into the anaerobic digestion tank after pH neutralization, the pH of the tank hardly changes and stable operation of the tank becomes possible.
- Embodiment 7 influent organic wastewater is treated with ozone and successively with alkali and, then, introduced into an anaerobic digestion tank after pH thereof is regulated.
- Embodiment 9 digested sludge drawn from an anaerobic digestion tank is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after pH thereof is regulated.
- digested sludge is thickened through solid-liquid separation, the thickened digested sludge is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after pH thereof is regulated.
- FIG. 21 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 5 shown in FIG. 15 is modified in such a way that conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to pH regulator 41 and pH regulator 41 is connected to anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the apparatus of the present embodiment conforms to that of Embodiment 5 shown in FIG. 15 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the thickened digested sludge in drain 5 is discharged through conduit 6 for disposing sludge, but part of the thickened digested sludge is introduced into ozonization tank 9 through conduit 7 and treated with ozone. Then, the thickened sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the thickened sludge treated with alkali is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 17 .
- the sludge solid component is introduced into pH regulator 41 via conduit 19 .
- the sludge dissolved component is mixed with calcium carbonate solution from the coagulant supply pump 22 to precipitate calcium phosphate. This precipitate is drawn out from conduit 25 and the remaining solution without phosphorus is introduced into pH regulator 41 via conduit 26 .
- pH regulator 41 the pH of the mixture comprising the sludge solid component and the phosphorus removed sludge dissolved component is measured and adjusted to 6 to 8 by adding hydrochloric acid.
- the pH adjusted mixture is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 5.
- digested sludge drawn from an anaerobic digestion tank is thickened and, then, synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in the thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- the pH of the sludge solid component separated in the solid-liquid separation tank after alkali treatment may be high due to residue of sodium hydroxide from the alkali treatment and if such sludge solid component is introduced into the anaerobic digestion tank, the pH inside the tank may suddenly change to make operations thereof unstable.
- sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, as the sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge throughout the treatments.
- a more stable and efficient treatment of organic sludge in which energy and resources are simultaneously recovered, is achieved by thickening the digested sludge drawn from the anaerobic digestion tank and treating the thickened sludge with the process comprising preceding ozone and succeeding alkali treatments, separation into sludge solid component and sludge dissolved component, phosphorus removal from the sludge dissolved component, pH neutralization of sludge solid component and/or sludge dissolved component, and introduction to the anaerobic digestion tank.
- the sludge solid component after solid-liquid separation and the sludge dissolved component after phosphorus removal are mixed and the pH of the mixture is adjusted.
- the pH of the sludge solid component after solid-liquid separation and that of the sludge dissolved component after phosphorus removal may be independently adjusted before introduction to the anaerobic digestion tank.
- either one of the pH of the sludge solid component after solid-liquid separation or that of the sludge dissolved component after phosphorus removal may be adjusted.
- FIG. 22 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 11 shown in FIG. 21 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 for alkali treated sludge is connected to pH regulator 41 in FIG. 22 .
- the apparatus of the present embodiment conforms to that of Embodiment 11 shown in FIG. 21 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the thickened digested sludge in drain 5 is discharged through conduit 6 for disposing sludge, but part of the thickened digested sludge is introduced into ozonization tank 9 through conduit 7 and treated with ozone.
- the thickened sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the thickened sludge treated with alkali is introduced into pH regulator 41 via drain 18 for alkali treated sludge.
- pH regulator 41 the pH of the thickened sludge treated with ozone and alkali is measured and adjusted to 6 to 8 by adding hydrochloric acid.
- the pH adjusted thickened sludge is introduced into anaerobic digestion tank 1 via conduit 42 for introducing pH regulated sludge.
- the process of the present embodiment conforms to that of Embodiment 11.
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge drawn from an anaerobic digestion tank is thickened and, then, synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- the pH of the thickened sludge treated with alkali may be high due to residue of sodium hydroxide from alkali treatment and if such thickened sludge is introduced into the anaerobic digestion tank, the pH inside the tank may suddenly change to make operations thereof unstable. According to the present embodiment, therefore, acid such as hydrochloric acid is added to the thickened sludge after alkali treatment to make the pH substantially neutral.
- acid such as hydrochloric acid is added to the thickened sludge after alkali treatment to make the pH substantially neutral.
- FIG. 23 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 1 shown in FIG. 11 is modified in such a way that rinse water supply conduit 44 connected to rinse water storage tank 47 is connected to conduit 19 for feeding treated sludge and conduit 19 is connected to hydro-extractor 43 .
- Hydro-extractor 43 is connected to anaerobic digestion tank 1 via conduit 46 for feeding rinsed sludge. Drain 45 for extracted water is also connected to hydro-extractor 43 .
- conduit 26 for feeding phosphorus removed water is connected to ion exchanger 48 and ion exchanger 48 is connected to anaerobic digestion tank 1 via conduit 49 for feeding ion exchanged water.
- the apparatus of the present embodiment conforms to that of Embodiment 1 shown in FIG. 11 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is sent to solid-liquid separation tank 17 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is sent to hydro-extractor 43 via conduit 19 . While sending, biologically treated water in rinse water storage tank 47 is supplied through conduit 44 and mixed with the sludge solid component flowing through the conduit 19 .
- hydro-extractor 43 the mixture is dehydrated, soluble ions in the sludge solid component are removed therefrom and the sludge solid component is rinsed.
- the rinsed sludge solid component is sent to anaerobic digestion tank 1 via conduit 46 , while the extracted water is discharged from drain 45 .
- phosphorus is removed therefrom and the sludge dissolved component after phosphorus recovery is introduced into ion exchanger 48 via conduit 26 .
- ion exchanger 48 ions in the sludge dissolved component after phosphorus recovery are removed and, then, the sludge dissolved component is introduced into anaerobic digestion tank 1 via conduit 49 for ion exchanged water.
- the process of the present embodiment conforms to that of Embodiment 1.
- organic sludge is synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in organic sludge such as fibers and cell walls, can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank may contain residue of sodium hydroxide from the alkali treatment and the sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, as the sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge throughout the treatments.
- the sodium ion concentration of the phosphorus removed sludge dissolved component is equal to or higher than that of the above sludge solid component after separation, introduction of such sludge dissolved component may also make the operations of the anaerobic digestion tank unstable. According to the present embodiment, therefore, the sludge solid component after solid-liquid separation is rinsed and the sludge dissolved component after phosphorus removal is ion-exchanged in order to remove the sodium ions. Since the sludge solid component and the sludge dissolved component are introduced into the anaerobic digestion tank after the removal of sodium ions, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the tank becomes possible.
- ions are removed from the sludge solid component and the sludge dissolved component after phosphorus removal and, then, the sludge solid component and the sludge dissolved component are introduced into the anaerobic digestion tank without further treatment.
- the pH thereof is neutralized before introduction into the anaerobic digestion tank as described in Embodiment 7, effects equal to or higher than those of the present embodiment may be obtained.
- the pH of the sludge solid component and/or sludge dissolved component may be adjusted before the ions are removed therefrom and introduced into the anaerobic digestion tank.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is sent to hydro-extractor 43 via drain 18 . While sending, biologically treated water in rinse water storage tank 47 is supplied through conduit 44 and mixed with the organic sludge flowing through the drain 18 .
- hydro-extractor 43 the mixture is dehydrated and soluble ions in the solids of the organic sludge are removed therefrom.
- the organic sludge rinsed in this way is sent to anaerobic digestion tank 1 via conduit 46 , while the extracted water is discharged from drain 45 .
- the process of the present embodiment conforms to that of Embodiment 13.
- the organic sludge may contain residue of sodium hydroxide from the alkali treatment and the sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such organic sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the organic sludge after alkali treatment is rinsed in order to remove sodium ions.
- the organic sludge after alkali treatment is rinsed in order to remove sodium ions.
- ions are removed from the organic sludge and, then, the organic sludge is introduced into the anaerobic digestion tank without further treatment.
- the pH of the organic sludge may be adjusted before the ions are removed from the organic sludge and introduced into the anaerobic digestion tank.
- Embodiment 13 influent organic wastewater is treated with ozone and successively with alkali and, then, introduced into an anaerobic digestion tank after inhibitors of anaerobic digestion are removed.
- digested sludge drawn from an anaerobic digestion tank is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after inhibitors of anaerobic digestion are removed.
- FIG. 25 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 3 shown in FIG. 13 is modified in such a way that rinse water supply conduit 44 connected to rinse water storage tank 47 is connected to conduit 19 for feeding treated sludge and conduit 19 is connected to hydro-extractor 43 .
- Hydro-extractor 43 is connected to anaerobic digestion tank 1 via conduit 46 for feeding rinsed sludge. Drain 45 for extracted water is also connected to hydro-extractor 43 .
- conduit 26 for feeding phosphorus removed water is connected to ion exchanger 48 and ion exchanger 48 is connected to anaerobic digestion tank 1 via conduit 49 for feeding ion exchanged water.
- the apparatus of the present embodiment conforms to that of Embodiment 3 shown in FIG. 13 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the digested sludge inside anaerobic digestion tank 1 is introduced into ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 17 .
- the sludge solid component is sent to hydro-extractor 43 via conduit 19 . While sending, biologically treated water in rinse water storage tank 47 is supplied through conduit 44 and mixed with the sludge solid component flowing through conduit 19 . In hydro-extractor 43 , the mixture is dehydrated and soluble ions in the sludge solid component are removed therefrom.
- the sludge solid component rinsed in this way is sent to anaerobic digestion tank 1 via conduit 46 , while the extracted water is discharged from drain 45 .
- the sludge dissolved component As for the sludge dissolved component, calcium carbonate solution is added by coagulant supply pump 22 and calcium phosphate is precipitated. This precipitate is drawn out via conduit 25 , while the remaining solution is introduced into ion exchanger 48 via conduit 26 . In ion exchanger 48 , ions in the sludge dissolved component after phosphorus recovery are removed and, then, the sludge dissolved component is introduced into anaerobic digestion tank 1 via conduit 49 for ion exchanged water. Other than those above, the process of the present embodiment conforms to that of Embodiment 3.
- digested sludge drawn from an anaerobic digestion tank is synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of the solids in digested sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances and, thereby, easily digested by sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank after alkali treatment may contain residue of sodium hydroxide from the alkali treatment and the sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, as the sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge throughout the treatments.
- a more stable and efficient treatment of organic sludge in which energy and resources are simultaneously recovered, is achieved by treating the digested sludge drawn from the anaerobic digestion tank with the process comprising preceding ozone and succeeding alkali treatments, separation into sludge solid component and sludge dissolved component, phosphorus removal from the sludge dissolved component, sodium ion removal from the sludge solid component and sludge dissolved component, and introduction to the anaerobic digestion tank.
- the sludge solid component is rinsed and the sludge dissolved component is ion-exchanged in order to remove sodium ions therefrom.
- other techniques for removing ions such as utilizing a reverse osmosis membrane, may be applicable.
- ions were removed from both the sludge solid component and the sludge dissolved component after phosphorus removal.
- ions may be removed from either one of the sludge solid component after solid-liquid separation or the sludge dissolved component after phosphorus removal.
- ions are removed from the sludge solid component and the sludge dissolved component and, then, the sludge solid component and the sludge dissolved component are introduced into the anaerobic digestion tank without further treatment.
- the pH thereof is neutralized before introduction into the anaerobic digestion tank as described in Embodiment 9, effects equal or higher than those of the present embodiment may be obtained.
- the pH of the sludge solid component and/or sludge dissolved component may be adjusted before the ions are removed therefrom and introduced into the anaerobic digestion tank.
- FIG. 26 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 15 shown in FIG. 25 . More specifically, solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out, rinse water supply conduit 44 connected to the rinse water storage tank 47 is connected to drain 18 for alkali treated sludge and drain 18 is connected to hydro-extractor 43 .
- the apparatus of the present embodiment conforms to that of Embodiment 15 shown in FIG. 25 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested with microorganisms in anaerobic digestion tank 1 .
- the digested sludge inside anaerobic digestion tank 1 is introduced into ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is sent to hydro-extractor 43 via drain 18 .
- the present embodiment is preferable when digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge drawn from an anaerobic digestion tank is synergistically affected by strong oxidation by ozone and decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- the digested sludge may contain residue of sodium hydroxide from the alkali treatment and the sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such digested sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the digested sludge after alkali treatment is rinsed in order to remove sodium ions.
- Embodiment 13 influent organic wastewater is treated with ozone and successively with alkali and, then, introduced into an anaerobic digestion tank after inhibitors of anaerobic digestion are removed.
- Embodiment 15 digested sludge drawn from an anaerobic digestion tank is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after inhibitors of anaerobic digestion are removed.
- digested sludge is thickened through solid-liquid separation, the thickened digested sludge is treated with ozone and successively with alkali and, then, introduced into the anaerobic digestion tank after inhibitors of anaerobic digestion are removed.
- conduit 26 for feeding phosphorus removed water is connected to ion exchanger 48 and ion exchanger 48 is connected to anaerobic digestion tank 1 via conduit 49 for feeding ion exchanged water.
- the apparatus of the present embodiment conforms to that of Embodiment 5 shown in FIG. 15 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested by microorganisms in anaerobic digestion tank 1 .
- the thickened digested sludge in drain 5 is discharged through conduit 6 for disposing sludge, but part of the thickened digested sludge is introduced into ozonization tank 9 through conduit 7 and treated with ozone. Then, the thickened sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- digested sludge from an anaerobic digestion tank is thickened and, then, synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by previously oxidizing the surface thereof with ozone.
- hardly soluble substances of solids in the thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, because sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge through the treatments.
- the sludge solid component after solid-liquid separation is rinsed and the sludge dissolved component after phosphorus removal is ion-exchanged in order to remove sodium ions. Since the sludge solid component and the sludge dissolved component are introduced into the anaerobic digestion tank after removal of sodium ions, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- the sludge solid component is rinsed and the sludge dissolved component is ion-exchanged in order to remove sodium ions therefrom.
- another technique for removing ions such as one utilizing a reverse osmosis membrane, may be applicable.
- ions may be removed from either the sludge solid component after solid-liquid separation or the sludge dissolved component after phosphorus removal depending on the effects on the anaerobic digestion tank.
- ions are removed from the sludge solid component and the sludge dissolved component and, then, the sludge solid component and the sludge dissolved component are introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 9 so that the effects of the present embodiment may be enhanced.
- pH of the sludge solid component and/or sludge dissolved component may be adjusted in advance and then, ions are removed therefrom prior to the introduction to the anaerobic digestion tank.
- FIG. 28 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 17 shown in FIG. 27 . More specifically, solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out, rinse water supply conduit 44 connected to rinse water storage tank 47 is connected to drain 18 for alkali treated sludge and the drain 18 is connected to the hydro-extractor 43 .
- the apparatus of the present embodiment conforms to that of Embodiment 17 shown in FIG. 27 .
- the thickened sludge treated with alkali is sent to hydro-extractor 43 via drain 18 .
- biologically treated water in rinse water storage tank 47 is supplied through conduit 44 and mixed with the thickened sludge flowing through drain 18 .
- the mixture is dehydrated so that soluble ions in the solids of the thickened sludge are removed therefrom, that is, the thickened sludge is rinsed.
- the rinsed thickened sludge is sent to anaerobic digestion tank 1 via conduit 46 , while extracted water is discharged from drain 45 .
- the process of the present embodiment conforms to that of Embodiment 17.
- the present embodiment is preferable when thickened sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge from an anaerobic digestion tank is thickened and, then, synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- the thickened sludge may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such thickened sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the thickened sludge after alkali treatment is rinsed in order to remove sodium ions. Since the thickened sludge is introduced into the anaerobic digestion tank after removal of sodium ions, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- ions are removed from the thickened sludge and, then, the thickened sludge is introduced into the anaerobic digestion tank without further treatment.
- pH of the thickened sludge may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 10 so that the effects of the present embodiment may be enhanced.
- pH of the thickened sludge may be adjusted in advance and then, ions are removed from the thickened sludge prior to the introduction to the anaerobic digestion tank.
- FIG. 29 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 1 shown in FIG. 11 is modified in such a way that the conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to dilution tank 52 and dilution tank 52 is connected to anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- diluent water supply conduit 51 is provided and connects diluent water storage tank 50 to dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 1 shown in FIG. 11 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into the ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is sent to solid-liquid separation tank 17 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into dilution tank 52 via conduit 19 .
- calcium carbonate solution is added by coagulant supply pump 22 .
- the precipitate i.e. calcium phosphate
- the precipitate is drawn out via conduit 25 , while the remaining solution is introduced into dilution tank 52 via conduit 26 .
- the mixture which comprises the sludge solid component and the sludge dissolved component where phosphorus is removed, is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that the concentration of soluble ion in the mixture is lowered. Thereafter, the diluted mixture is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 1.
- organic sludge is synergistically affected by strong oxidation by ozone as well as decomposition with alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- hardly soluble substances of solids in organic sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank after alkaline treatment may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, because sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge through the treatments.
- the sludge solid component after solid-liquid separation and the sludge dissolved component after phosphorus removal are diluted by adding biologically treated water so that sodium ion concentration thereof is lowered. Since the sludge solid component and the sludge dissolved component of lower sodium ion concentration are introduced into the anaerobic digestion tank, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- the separated sludge solid component and the sludge dissolved component from which phosphorus is removed are mixed and the mixture is diluted to lower the sodium ion concentration.
- the sludge solid component and the sludge dissolved component may be diluted independently and then introduced to the anaerobic digestion tank.
- either the sludge solid component or the sludge dissolved component may be diluted.
- the sludge solid component and the sludge dissolved component from which phosphorus is removed are diluted and, then, introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 7 so that the effects of the present embodiment may be enhanced.
- pH of the sludge solid component and/or sludge dissolved component may be adjusted in advance and then, diluted prior to the introduction to the anaerobic digestion tank.
- FIG. 30 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 19 shown in FIG. 29 .
- solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 is connected to dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 19 shown in FIG. 29 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 and treated with ozone.
- the organic sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the organic sludge treated with alkali is sent to dilution tank 52 via drain 18 for alkali treated sludge.
- the organic sludge treated with ozone and alkali is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that the concentration of soluble ion in the organic sludge is lowered. Thereafter, the diluted sludge is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 19.
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- organic sludge is synergistically affected by strong oxidation by ozone and decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- hardly soluble substances of solids in organic sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- This improvement in solubilization is much greater than that obtained with ozone treatment alone or alkali treatment alone and, importantly, greater than the sum of these improvements so yield of methane is greatly improved and sludge to be disposed is greatly reduced.
- the organic sludge may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such organic sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the organic sludge after alkali treatment is diluted by adding biologically treated water so that sodium ion concentration thereof is lowered. Since the organic sludge of lower sodium ion concentration is introduced into the anaerobic digestion tank, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- the organic sludge is diluted and then, introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 8 so that the effects of the present embodiment may be enhanced.
- pH of the organic sludge may be adjusted in advance, the organic sludge is diluted in order to decrease the sodium ion concentration prior to the introduction to the anaerobic digestion tank.
- Embodiment 19 influent organic wastewater is treated with ozone and successively with alkali and then introduced into an anaerobic digestion tank after the concentration of the inhibitor against anaerobic digestion is lowered.
- digested sludge from an anaerobic digestion tank is treated with ozone and successively with alkali and then introduced into the anaerobic digestion tank after the concentration of the inhibitor against anaerobic digestion is lowered.
- FIG. 31 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 3 shown in FIG. 13 is modified in such a way that conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to dilution tank 52 and dilution tank 52 is connected to anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- diluent water supply conduit 51 is provided and connects diluent water storage tank 50 to dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 3 shown in FIG. 13 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into the anaerobic digestion tank 1 and digested by microorganisms in the anaerobic digestion tank 1 .
- the digested sludge inside the anaerobic digestion tank 1 is introduced into ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 17 .
- the sludge solid component is introduced into dilution tank 52 via conduit 19 .
- calcium carbonate solution is added by coagulant supply pump 22 .
- the precipitate, i.e. calcium phosphate is drawn out via conduit 25 , while the remaining solution is introduced into dilution tank 52 via conduit 26 .
- the mixture which comprises the sludge solid component and the sludge dissolved component from which phosphorus is removed, is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that the concentration of soluble ion in the mixture is lowered. Thereafter, the diluted mixture is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 3.
- digested sludge from an anaerobic digestion tank is synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- hardly soluble substances of solids in digested sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component in which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, because sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge through the treatments.
- the sodium ion concentration of the phosphorus removed sludge dissolved component is equal to or higher than that of the sludge solid component after the solid-liquid separation
- introduction of such sludge dissolved component may also make the operations of the anaerobic digestion tank unstable. According to the present embodiment, therefore, the sludge solid component after solid-liquid separation and the sludge dissolved component after phosphorus removal are diluted by adding biologically treated water so that sodium ion concentration thereof is lowered.
- the separated sludge solid component and the separated sludge dissolved component from which phosphorus is removed are mixed and the mixture is diluted to lower sodium ion concentration.
- the sludge solid component and the sludge dissolved component are diluted independently to decrease the sodium ion concentration before the introduction to the anaerobic digestion tank.
- either the sludge solid component or the sludge dissolved component may be diluted depending on the effects on the anaerobic digestion tank.
- the separated sludge solid component and the separated sludge dissolved component from which phosphorus is removed are diluted and then introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 9 so that the effects of the present embodiment may be enhanced.
- pH of the sludge solid component and/or sludge dissolved component may be adjusted in advance and then diluted in order to decrease the sodium ion concentration prior to the introduction to the anaerobic digestion tank.
- FIG. 32 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 21 shown in FIG. 31 . More specifically, solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 is connected to dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 21 shown in FIG. 31 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into the anaerobic digestion tank 1 and digested by microorganisms in anaerobic digestion tank 1 .
- the digested sludge inside anaerobic digestion tank 1 is introduced into the ozonization tank 9 through conduit 34 and treated with ozone.
- the digested sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the digested sludge treated with alkali is sent to dilution tank 52 via drain 18 for alkali treated sludge.
- the digested sludge treated with ozone and alkali is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that concentration of soluble ion in the digested sludge is lowered. Thereafter, the diluted sludge is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 21.
- the digested sludge may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such digested sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the digested sludge after alkali treatment is diluted by adding biologically treated water so that sodium ion concentration thereof is lowered. Since the digested sludge of lower sodium ion concentration is introduced into the anaerobic digestion tank, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- the digested sludge is diluted and then introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 10 so that the effects of the present embodiment may be enhanced.
- pH of the digested sludge may be adjusted in advance and, then, the digested sludge is diluted to decrease the sodium ion concentration prior to the introduction to the anaerobic digestion tank.
- Embodiment 19 influent organic wastewater is treated with ozone and successively with alkali and then introduced into an anaerobic digestion tank after the concentration of the inhibitor against anaerobic digestion is lowered.
- Embodiment 21 digested sludge from an anaerobic digestion tank is treated with ozone and successively with alkali and then introduced into the anaerobic digestion tank after the concentration of the inhibitor against anaerobic digestion is lowered.
- digested sludge is thickened through solid-liquid separation, the thickened digested sludge is treated with ozone and successively with alkali and then introduced into the anaerobic digestion tank after the concentration of the inhibitor against anaerobic digestion is lowered.
- FIG. 33 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- the apparatus of Embodiment 5 shown in FIG. 15 is modified in such a way that conduit 19 for feeding treated sludge and conduit 26 for feeding phosphorus removed water are connected to dilution tank 52 and dilution tank 52 is connected to the anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- diluent water supply conduit 51 is provided and connects diluent water storage tank 50 to the dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 5 shown in FIG. 15 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested by microorganisms in anaerobic digestion tank 1 .
- the thickened digested sludge in drain 5 is discharged through conduit 6 for disposing sludge, but part of the thickened digested sludge is introduced into the ozonization tank 9 through conduit 7 and treated with ozone.
- the thickened sludge treated with ozone is introduced into the alkalization tank 12 and treated with alkali.
- the thickened sludge treated with alkali is separated into sludge solid component and sludge dissolved component at solid-liquid separation tank 17 .
- the sludge solid component is introduced into dilution tank 52 via conduit 19 .
- calcium carbonate solution is added by the coagulant supply pump 22 .
- the precipitate, i.e. calcium phosphate is drawn out via conduit 25 , while the remaining solution is introduced into dilution tank 52 via conduit 26 .
- the mixture which comprises the sludge solid component and the sludge dissolved component from which phosphorus is removed, is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that the concentration of the soluble ion in the mixture is lowered. Thereafter, the diluted mixture is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 5.
- digested sludge from an anaerobic digestion tank is thickened and then synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- hardly soluble substances of solids in the thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- the sludge solid component separated in the solid-liquid separation tank after alkali treatment may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such sludge solid component is introduced into the anaerobic digestion tank. Moreover, sludge dissolved component from which phosphorus is removed is preferably introduced into the anaerobic digestion tank to produce methane effectively, because the sludge dissolved component contains a great deal of organic substances that are eluted out from the sludge through the treatments.
- the sodium ion concentration of the phosphorus removed sludge dissolved component is equal to or higher than that of the sludge solid component after the solid-liquid separation
- introduction of such sludge dissolved component may also make the operations of the anaerobic digestion tank unstable. According to the present embodiment, therefore, the sludge solid component after solid-liquid separation and the sludge dissolved component after phosphorus removal are diluted by adding biologically treated water so that sodium ion concentration thereof is lowered.
- the separated sludge solid component and the sludge dissolved component from which phosphorus is removed are mixed and the mixture is diluted to lower sodium ion concentration.
- the separated sludge solid component and the separated sludge dissolved component from which phosphorus is removed are diluted independently to decrease the sodium ion concentration before the introduction to the anaerobic digestion tank.
- either the sludge solid component or the sludge dissolved component may be diluted.
- the sludge solid component and the sludge dissolved component are diluted and then introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 11 so that the effects of the present embodiment may be enhanced.
- pH of the sludge solid component and/or sludge dissolved component may be adjusted in advance and, then, diluted prior to the introduction to the anaerobic digestion tank.
- FIG. 34 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 23 shown in FIG. 33 . More specifically, solid-liquid separation tank 17 , conduit 19 , drain 20 , coagulant storage tank 21 , coagulant supply pump 22 , coagulant supply conduit 23 , phosphorus recovery tank 24 , conduit 25 for recovering phosphorus and conduit 26 for feeding phosphorus removed water are left out and drain 18 is connected to dilution tank 52 .
- the apparatus of the present embodiment conforms to that of Embodiment 23 shown in FIG. 33 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 and digested by microorganisms in anaerobic digestion tank 1 .
- the thickened digested sludge in drain 5 is discharged through conduit 6 for disposing sludge, but part of the thickened digested sludge is introduced into ozonization tank 9 through conduit 7 and treated with ozone.
- the thickened sludge treated with ozone is introduced into alkalization tank 12 and treated with alkali.
- the thickened sludge treated with alkali is sent to dilution tank 52 via drain 18 for alkali treated sludge.
- the thickened sludge treated with ozone and alkali is diluted by injecting biologically treated water stored in diluent water storage tank 50 through supply conduit 51 so that the concentration of soluble ion in the thickened sludge is lowered.
- the diluted sludge is introduced into anaerobic digestion tank 1 via conduit 53 for feeding diluted sludge.
- the process of the present embodiment conforms to that of Embodiment 23.
- the present embodiment is preferable when thickened sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge from an anaerobic digestion tank is thickened and then synergistically affected by strong oxidation by ozone as well as decomposition by alkali.
- decomposition of organic substances by alkali treatment is highly enhanced by oxidizing the surface thereof with ozone prior to alkali treatment.
- the thickened sludge may contain residue of sodium hydroxide from the alkali treatment and sodium ions inhibit the activity of the microorganisms for digestion. Accordingly, the operations of the anaerobic digestion tank may become unstable if such thickened sludge is introduced into the anaerobic digestion tank. According to the present embodiment, therefore, the thickened sludge after alkali treatment is diluted by adding biologically treated water so that sodium ion concentration thereof is lowered. Since the thickened sludge of lower sodium ion concentration is introduced into the anaerobic digestion tank, deactivation of the microorganisms by sodium ions hardly occurs and stable operation of the anaerobic digestion tank becomes possible.
- the thickened sludge is diluted and then introduced into the anaerobic digestion tank without further treatment.
- pH thereof may be adjusted to approximately neutral before the introduction to the anaerobic digestion tank as described in Embodiment 12 so that the effects of the present embodiment may be enhanced.
- pH of the thickened sludge may be adjusted in advance and then the thickened sludge is diluted prior to the introduction to the anaerobic digestion tank.
- FIG. 35 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- ozonization tank 9 and solid-liquid separation tank 17 are arranged between anaerobic digestion tank 1 and organic wastewater feed conduit 2 .
- Ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- Hydrogen peroxide storage tank 28 is also connected to ozonization tank 9 via hydrogen peroxide supply conduit 30 and hydrogen peroxide supply conduit 30 is provided with a hydrogen peroxide supply pump 29 .
- Ozonization tank 9 is connected to solid-liquid separation tank 17 via drain 31 for ozone treated sludge and solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge.
- anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for discharging digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits, one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into the ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the ozone injection rate is preferably 0.01 to 0.10 g-O 3 /g-SS and more preferably 0.03 to 0.07 g-O 3 /g-SS.
- ozone injection rate of lower than 0.01 g-O 3 /g-SS organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with such lower ozone injection rate.
- a higher ozone injection rate enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with an ozone injection rate higher than 0.10 g-O 3 /g-SS. Therefore, an ozone injection rate higher than 0.10 g-O 3 /g-SS is considered uneconomical.
- the precipitate, i.e. calcium phosphate, in phosphorus recovery tank 24 is separated from the solution and drawn out from conduit 25 , and the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- the digested sludge in anaerobic digestion tank 1 is discharged from drain 3 and separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas generated in anaerobic digestion tank 1 is recovered from vent 27 .
- radicals such as OH radicals, which have stronger oxidization and decomposition effects than ozone, are generated.
- hardly soluble substances of solids in organic sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by the sludge in the anaerobic digestion tank.
- the soluble amount of solids in the organic sludge is increased and yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared with the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- FIG. 36 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 25 shown in FIG. 35 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects the ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- pump 29 works to supply hydrogen peroxide from hydrogen peroxide storage tank 28 to ozonization tank 9 via conduit 30 so that the organic sludge is treated with ozone in the presence of hydrogen peroxide.
- the digested sludge in anaerobic digestion tank 1 is discharged from drain 3 and separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and sludge solid component are discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals are generated and, owing to the extremely strong oxidization effect of radicals, hardly soluble substances of solids in organic sludge, such as fibers and cell walls, can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- the soluble amount of solids in the organic sludge is increased and the yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced as compared with the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- Embodiment 25 Another apparatus embodying the present invention and a process of treating organic wastewater with the apparatus is described.
- influent organic wastewater is treated with ozone in the presence of hydrogen peroxide.
- digested sludge from the anaerobic digestion tank is treated with ozone in the presence of hydrogen peroxide.
- FIG. 37 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Conduit 34 for discharging digested sludge is connected to anaerobic digestion tank 1 and leads to ozonization tank 9 .
- the ozonization tank 9 is connected to solid-liquid separation tank 17 via drain 31 for ozone treated sludge.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge.
- Solid-liquid separation tank 17 is also connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- ozone generator 10 and hydrogen peroxide storage tank 28 are connected to ozonization tank 9 via ozone gas supply conduit 11 and hydrogen peroxide supply conduit 30 , respectively.
- Hydrogen peroxide supply conduit 30 is equipped with hydrogen peroxide supply pump 29 .
- Solid-liquid separation tank 17 is connected to phosphorus recovery tank 24 via drain 20 as described above, coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for discharging digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits, one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to anaerobic digestion tank 1 , and conduit 7 for returning sludge is connected to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in the anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the digested sludge inside the anaerobic digestion tank 1 is sent to ozonization tank 9 through conduit 34 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- pump 29 works to supply hydrogen peroxide from hydrogen peroxide storage tank 28 to ozonization tank 9 via conduit 30 and the digested sludge is treated with ozone in the presence of hydrogen peroxide.
- the digested sludge After being treated with ozone in the presence of hydrogen peroxide, the digested sludge is sent to solid-liquid separation tank 17 via drain 31 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms. Meanwhile, the sludge dissolved component rich in phosphorus is introduced into the phosphorus recovery tank 24 via drain 20 .
- coagulant supply pump 22 is operated to supply calcium carbonate solution stored in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by the coagulant supply pump 22 via coagulant supply conduit 23 and phosphorus in the sludge dissolved component is precipitated as calcium phosphate.
- the precipitate in phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , and the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- the soluble amount of solids in the organic sludge is increased and the yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared with the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- FIG. 38 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 27 shown in FIG. 37 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the digested sludge inside anaerobic digestion tank 1 is sent to ozonization tank 9 via conduit 34 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- pump 29 works to supply hydrogen peroxide from hydrogen peroxide storage tank 28 to ozonization tank 9 via conduit 30 and the digested sludge is treated with ozone in the presence of hydrogen peroxide.
- the present embodiment is preferable when digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals are generated and, owing to the extremely strong oxidization effect of radicals, hardly soluble substances of solids in organic sludge, such as fibers and cell walls, can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- the soluble amount of solids in the organic sludge is increased and the yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared with the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- Embodiment 25 influent organic wastewater is treated with ozone in presence of hydrogen peroxide.
- Embodiment 27 digested sludge from the anaerobic digestion tank is treated with ozone in the presence of hydrogen peroxide.
- digested sludge is thickened through solid-liquid separation and, then, the thickened sludge is treated with ozone in the presence of hydrogen peroxide.
- FIG. 39 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for discharging digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits, one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to ozonization tank 9 , and conduit 7 for returning sludge is connected to ozonization tank 9 .
- Ozonization tank 9 is connected to solid-liquid separation tank 17 via drain 31 for ozone treated sludge.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge and connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water.
- the phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- the anaerobic digestion tank 1 has vent 27 for digester gas.
- ozone generator 10 and hydrogen peroxide storage tank 28 are connected to ozonization tank 9 via ozone gas supply conduit 11 and hydrogen peroxide supply conduit 30 , respectively.
- the hydrogen peroxide supply conduit 30 is equipped with hydrogen peroxide supply pump 29 .
- the solid-liquid separation tank 17 is connected to phosphorus recovery tank 24 via drain 20 as described above, coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- ozonization tank 9 the thickened sludge from conduit 7 is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- pump 29 works to supply hydrogen peroxide from hydrogen peroxide storage tank 28 to ozonization tank 9 via conduit 30 and the thickened sludge is treated with ozone in the presence of hydrogen peroxide.
- the thickened sludge After being treated with ozone in the presence of hydrogen peroxide, the thickened sludge is sent to solid-liquid separation tank 17 via drain 31 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms. Meanwhile, the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- coagulant supply pump 22 is operated to supply calcium carbonate solution in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by the coagulant supply pump 22 via coagulant supply conduit 23 and phosphorus in the sludge dissolved component is precipitated as calcium phosphate.
- the precipitate in phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , and the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- radicals such as OH radicals, which have stronger oxidization and decomposition effects than ozone, are generated.
- hardly soluble substances of solids in thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- the soluble amount of solids in the thickened sludge is increased and the yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared with the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- FIG. 40 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 29 shown in FIG. 39 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via the conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component at solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- ozonization tank 9 the thickened sludge from conduit 7 is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- pump 29 works to supply hydrogen peroxide from the hydrogen peroxide storage tank 28 to ozonization tank 9 via conduit 30 and the thickened sludge is treated with ozone in the presence of hydrogen peroxide.
- the thickened sludge After being treated with ozone in the presence of hydrogen peroxide, the thickened sludge is introduced into anaerobic digestion tank 1 via drain 31 and anaerobically digested by microorganisms.
- the present embodiment is preferable when digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals such as OH radicals, which have stronger oxidization and decomposition effects than ozone, are generated.
- hardly soluble substances of solids in thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- solubilization of solids in the thickened sludge is enhanced and the yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared to the case of ozone treatment without hydrogen peroxide or addition of hydrogen peroxide without ozone treatment.
- FIG. 41 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- ozonization tank 9 and solid-liquid separation tank 17 are arranged between anaerobic digestion tank 1 and organic wastewater feed conduit 2 .
- Ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- the top surface of ozonization tank 9 is designed to let in ultraviolet from UV radiator 32 through, e.g. a transparent window.
- Solid-liquid separation tank 17 is also connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- Coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for drawing digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits; one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to the anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the organic sludge inside the ozonization tank 9 is exposed to UV radiation from UV radiator 32 so that the organic sludge is treated with ozone under UV radiation.
- the wavelength of UV radiation is preferably 180 to 300 nm
- output of UV radiation is preferably 5.0 to 200 W
- exposure to the UV radiation is preferably 5 to 30 minutes.
- wavelength of UV radiation is longer than 300 nm
- organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with the UV radiation of such a longer wavelength.
- shorter wavelength enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with a wavelength shorter than 180 nm. Therefore, wavelength shorter than 180 nm is considered uneconomical.
- the ozone injection rate is preferably 0.01 to 0.10 g-O 3 /g-SS and more preferably 0.03 to 0.07 g-O 3 /g-SS.
- an ozone injection rate smaller than 0.01 g-O 3 /g-SS organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with such smaller ozone injection rate.
- larger ozone injection rate enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with an ozone injection rate larger than 0.10 g-O 3 /g-SS. Therefore, an ozone injection rate larger than 0.10 g-O 3 /g-SS is considered uneconomical.
- the digested sludge in anaerobic digestion tank 1 is discharged from drain 3 and separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- this embodiment relates to an apparatus for treating organic wastewater comprising a means for treating organic wastewater with ozone under UV radiation and an anaerobic digestion tank for anaerobically digesting the ozone treated organic wastewater.
- This embodiment also relates to a process for treating organic wastewater by anaerobic digestion, which comprises treating organic wastewater with ozone under UV radiation and introducing said ozone treated organic wastewater into an anaerobic digestion tank.
- FIG. 42 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 31 shown in FIG. 41 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into ozonization tank 9 via conduit 2 .
- the organic sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the organic sludge inside ozonization tank 9 is exposed to UV radiation from UV radiator 32 and the organic sludge is treated with ozone under UV radiation.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the present embodiment is preferable when organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- organic sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals are generated and, owing to the extremely strong oxidization effect of radicals, hardly soluble substances of solids in organic sludge, such as fibers and cell walls, can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- solubility of solids in the organic sludge is increased and yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced as compared with the case of ozone treatment without UV radiation or UV radiation without ozone treatment.
- Embodiment 31 Another apparatus embodying the present invention and a process of treating organic wastewater with the apparatus is described.
- influent organic wastewater is treated with ozone under UV radiation.
- digested sludge drawn from the anaerobic digestion tank is treated with ozone under UV radiation.
- FIG. 43 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Conduit 34 for drawing digested sludge is connected to anaerobic digestion tank 1 and leads to ozonization tank 9 .
- Ozonization tank 9 is connected to solid-liquid separation tank 17 via drain 31 for ozone treated sludge.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge.
- Solid-liquid separation tank 17 is also connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water and phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- the top surface of the ozonization tank 9 is designed to let in ultraviolet radiation from UV radiator 32 through, e.g. a transparent window.
- Solid-liquid separation tank 17 is connected to phosphorus recovery tank 24 via drain 20 as described above, and coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is discharged from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component at solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the digested sludge inside anaerobic digestion tank 1 is drawn out from the conduit 34 and sent to ozonization tank 9 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the organic sludge inside ozonization tank 9 is exposed to UV radiation from UV radiator 32 so that the organic sludge is treated with ozone under UV radiation.
- the digested sludge is sent to solid-liquid separation tank 17 via drain 31 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms.
- the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- calcium carbonate solution in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by coagulant supply pump 22 via coagulant supply conduit 23 and phosphorus in the sludge dissolved component is precipitated as calcium phosphate.
- the precipitate in the phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 and the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- FIG. 44 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 33 shown in FIG. 43 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to anaerobic digestion tank 1 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the digested sludge inside anaerobic digestion tank 1 is drawn out from conduit 34 and sent to ozonization tank 9 .
- the digested sludge is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the organic sludge inside ozonization tank 9 is exposed to UV radiation from UV radiator 32 so that the organic sludge is treated with ozone under UV radiation.
- the digested sludge After being treated with ozone under UV radiation, the digested sludge is introduced into anaerobic digestion tank 1 via drain 31 and anaerobically digested by microorganisms.
- the present embodiment is preferable when digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals such as OH radicals, which have stronger oxidization and decomposition effects than ozone, are generated.
- hardly soluble substances of solids in digested sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- solubility of solids in the organic sludge is increased and yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced, as compared with the case of ozone treatment without UV radiation or UV radiation without ozone treatment.
- Embodiment 31 influent organic wastewater is treated with ozone under UV radiation.
- Embodiment 33 digested sludge drawn from the anaerobic digestion tank is treated with ozone under UV radiation.
- digested sludge is thickened through solid-liquid separation and, then, the thickened sludge is treated with ozone under UV radiation.
- FIG. 45 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- organic wastewater feed conduit 2 is connected to anaerobic digestion tank 1 .
- Anaerobic digestion tank 1 is connected to solid-liquid separation tank 4 via drain 3 for drawing digested sludge.
- Drain 5 for thickened sludge and drain 8 for supernatant water are connected to solid-liquid separation tank 4 .
- Drain 5 branches into two conduits; one, i.e. conduit 6 , is for disposing sludge and the other, i.e. conduit 7 , is for returning sludge to ozonization tank 9 .
- Anaerobic digestion tank 1 has vent 27 for digester gas.
- the ozonization tank 9 is connected to solid-liquid separation tank 17 via drain 31 for ozone treated sludge.
- Solid-liquid separation tank 17 is connected to anaerobic digestion tank 1 via conduit 19 for feeding treated sludge and connected to phosphorus recovery tank 24 via drain 20 for phosphorus containing water.
- Phosphorus recovery tank 24 is connected to anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- ozone generator 10 is connected to ozonization tank 9 via ozone gas supply conduit 11 .
- the top surface of ozonization tank 9 is designed to let in ultraviolet radiation from UV radiator 32 through, e.g. a transparent window.
- Solid-liquid separation tank 17 is connected to phosphorus recovery tank 24 via drain 20 as described above, coagulant supply conduit 23 equipped with coagulant supply pump 22 connects coagulant storage tank 21 to drain 20 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from the vent 27 .
- ozonization tank 9 the thickened sludge from conduit 7 is treated with ozone by injecting ozone gas from ozone generator 10 into ozonization tank 9 via conduit 11 .
- the digested sludge inside ozonization tank 9 is exposed to UV radiation from UV radiator 32 so that the digested sludge is treated with ozone under UV radiation.
- the thickened sludge is sent to solid-liquid separation tank 17 via drain 31 and separated into sludge solid component and sludge dissolved component.
- the sludge solid component is introduced into anaerobic digestion tank 1 via conduit 19 and anaerobically digested by microorganisms.
- the sludge dissolved component rich in phosphorus is introduced into phosphorus recovery tank 24 via drain 20 .
- calcium carbonate solution in coagulant storage tank 21 is injected into and mixed with the phosphorus containing solution flowing through drain 20 by coagulant supply pump 22 via coagulant supply conduit 23 and phosphorus in the sludge dissolved component is precipitated as calcium phosphate.
- the precipitate in phosphorus recovery tank 24 i.e. calcium phosphate, is separated from the solution and drawn out from conduit 25 , and the remaining solution without phosphorus is introduced into anaerobic digestion tank 1 via conduit 26 for feeding phosphorus removed water.
- FIG. 46 is a diagram of an apparatus embodying the present invention and shows a process flow of treating organic wastewater with the apparatus.
- components for recovering phosphorus are left out from the apparatus of Embodiment 35 shown in FIG. 45 . More specifically, phosphorus recovery tank 24 , solid-liquid separation tank 17 and coagulant storage tank 21 are left out and drain 31 for ozone treated sludge connects ozonization tank 9 to anaerobic digestion tank 1 .
- organic sludge from a water treatment plant which is a mixture of raw sludge from a primary sedimentation tank and excess sludge from an aeration tank, is introduced into anaerobic digestion tank 1 via conduit 2 .
- the organic sludge is digested by microorganisms in anaerobic digestion tank 1 and, then, the sludge inside anaerobic digestion tank 1 is drawn out from drain 3 .
- the sludge from drain 3 is separated into sludge solid component and sludge dissolved component in solid-liquid separation tank 4 .
- the sludge dissolved component is discharged from drain 8 for supernatant water and the sludge solid component is discharged from drain 5 for thickened sludge.
- the sludge solid component in drain 5 is discharged through conduit 6 for disposing sludge, but part of the sludge solid component is returned to ozonization tank 9 through conduit 7 for returning sludge. Meanwhile, the digester gas in anaerobic digestion tank 1 is recovered from vent 27 .
- the thickened sludge After being treated with ozone under UV radiation, the thickened sludge is introduced into anaerobic digestion tank 1 via drain 31 and anaerobically digested by microorganisms.
- the present embodiment is preferable when digested sludge contains little phosphorus and recovering energy from the sludge is a priority.
- radicals such as OH radicals, which have stronger oxidization and decomposition effects than ozone, are generated.
- hardly soluble substances of solids in thickened sludge, such as fibers and cell walls can be denatured and converted into easily soluble substances which can be easily decomposed by sludge in the anaerobic digestion tank.
- solubility of solids in the thickened sludge is increased and yield of methane is greatly increased and, correspondingly, sludge to be disposed is greatly reduced as compared with the case of ozone treatment without UV radiation or UV radiation without ozone treatment.
- the organic wastewater is anaerobically digested in one anaerobic digestion tank.
- the present invention is not limited thereto.
- the apparatus and the process according to the present invention are also applicable to the case in which two tanks, i.e. one for producing acids and the other for producing methane, are utilized to anaerobically digest the organic wastewater and the same effects as described above such as efficient denaturation of hardly soluble substances and increase of the recovery rate of phosphorus can be obtained.
- the phosphorus removed water is returned to the anaerobic digestion tank 1 via conduit 26 in the above Embodiments, the phosphorus removed water may be separately treated without returning to anaerobic digestion tank 1 .
- a mixture comprising raw sludge and excess sludge both from a water treatment plant is treated as organic wastewater.
- the organic wastewater to be treated is not limited thereto and the same or greater effects as those of the above Embodiments can be obtained even when treating sludge, waste and effluent rich in organic substances, such as raw sludge from a water treatment plant, excess sludge from the same, raw garbage, food waste, animal waste, human waste, industrial waste and mixture thereof.
- sodium hydroxide is used for alkali treatment in the above Embodiments 1 to 36 and the following Examples, another alkali agent such as potassium hydroxide may be applicable.
- UV ray is radiated through the top surface of the ozonization tank where the transparent windows is provided.
- transparent window(s) may be provided at the side or bottom of the ozonization tank to introduce UV radiation.
- the effect equal to or higher than that of the above Embodiments can also be obtained even when the UV radiator is arranged inside the ozonization tank.
- Excess sludge was drawn out from a wastewater treatment plant, treated with ozone and, then, treated with alkali.
- the ozone injection rate was 0.05 g-O 3 /g-SS.
- sodium hydroxide was added and pH 12 was maintained for 10 minutes.
- 1.0 L of digested sludge having a TS concentration of about 25,000 mg/L was drawn out from an aerobic digestion tank and, then, introduced into a culture flask having an effective volume of 3.0 L.
- 1.0 L of the above treated sludge (sludge treated with ozone and alkali) of which the pH was adjusted to approximately neutral and the TS concentration was adjusted to about 25,000 mg/L was introduced into the culture flask.
- 2.0 L of the sludge mixture having a TS concentration of 25,000 mg/L obtained in this way was anaerobically digested at 50° C. (Example 1).
- the above excess sludge was treated with ozone (without alkali treatment) or treated with alkali (without ozone treatment).
- the ozone injection rate was 0.05 g-O 3 /g-SS in this ozone treatment and pH 12 was maintained for 10 minutes in this alkali treatment.
- 1.0 L of an aerobically digested sludge having a TS concentration of about 25,000 mg/L was introduced into a culture flask having an effective volume of 3.0 L.
- 1.0 L of the above treated sludge (sludge treated with ozone or sludge treated with alkali) of which the pH was approximately neutral and the TS concentration was about 25,000 mg/L was introduced into the culture flask.
- 2.0 L of a sludge mixture having a TS concentration of 25,000 mg/L obtained in this way was anaerobically digested at 50° C. (Comparative Example 1 or 2).
- Examples 1 to 3 and Comparative Examples 1 to 3 variation in TS concentration was shown in FIG. 1 and amount of digester gas produced (in total) was shown in FIG. 2 .
- white circles represent Comparative Example 1 in which sludge was not treated
- white squares represent Comparative Example 2 in which sludge was treated with alkali alone
- white triangles represent Comparative Example 3 in which sludge was treated with ozone alone
- black circles represent Example 1 in which the pH of the sludge treated with ozone and alkali was adjusted to neutral
- black squares represent Example 2 in which the pH of the sludge treated with ozone and alkali was not adjusted to neutral
- white diamonds represent Example 3 in which sludge treated with ozone and alkali was rinsed, respectively.
- decomposition of solids in the sludge advances and the TS concentration decreases over time.
- decomposition of solids is promoted and the TS concentration decreases rapidly.
- decomposition of solids is further promoted and TS concentration is significantly decreased.
- decrease in TS concentration for 15 days is about 3,000 mg/L for the sludge treated with ozone alone and about 1,500 mg/L for the sludge treated with alkali alone
- that for the sludge treated with ozone and alkali in combination is about 8,000 mg/L which is greater than the sum of the above decreases of ozone treatment alone and alkali treatment alone.
- the pH of the sludge treated with ozone and alkali is preferably adjusted to approximately neutral to ensure the above decrease in TS concentration, i.e. effect of decomposing the sludge.
- sodium ions are preferably removed, for example, by rinsing the sludge or the solution is diluted, to ensure the above decrease in TS concentration, i.e. effect of decomposing the sludge.
- the amount of produced digester gas from the sludge treated with ozone and alkali in combination is greater than that from ozone treated sludge or alkali treated sludge. Since the amount of produced digester gas from the sludge treated with ozone and alkali in combination is greater than the sum of the yields from ozone treated sludge and alkali treated sludge, the combination of ozone and alkali treatments has found to be synergistic. Furthermore, the amount of produced digester gas from the rinsed sludge increased as compared with the case without rinsing, indicating the remarkable effect of removing sodium ion.
- Eluted phosphorus in the supernatant water was precipitated as calcium phosphate by adding and mixing calcium carbonate solution and recovered as solid phosphorus by centrifugal separation. The amount of recovered phosphorus was greatest when the sludge was treated with ozone and alkali in combination.
- the process of the present invention in which ozone treatment and succeeding alkali treatment are combined, is highly effective in decreasing the solids in the sludge, i.e. decomposition, promoting production of digester gas and eluting and recovering phosphorus in the sludge.
- the above effects can be increased by adjusting the pH of the sludge to neutral and/or removing sodium ions of alkali treatment from the sludge.
- organic substances eluted along with phosphorus can be converted into methane and generation of digester gas can be increased by anaerobically digesting after removing sodium ions added in alkali treatment and/or adjusting the pH of the phosphorus removed water.
- the ozone injection rate is preferably 0.01 to 0.10 g-O 3 /g-SS and more preferably 0.03 to 0.07 g-O 3 /g-SS.
- an ozone injection rate smaller than 0.01 g-O 3 /g-SS organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with such a small ozone injection rate.
- a larger ozone injection rate enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with an ozone injection rate larger than 0.10 g-O 3 /g-SS. Therefore, an ozone injection rate larger than 0.10 g-O 3 /g-SS is considered uneconomical.
- the sludge is preferably treated with alkali for 5 to 30 minutes maintaining pH within a range of 9 to 13.
- a pH smaller than 9 organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with a pH smaller than 9.
- a higher alkalinity enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with a pH higher than 13. Therefore, a pH higher than 13 is considered uneconomical.
- Example 4 and Comparative Examples 4 to 6 variation in TS concentration over time was shown in FIG. 4 and amount of digester gas produced (in total) was shown in FIG. 5 .
- white circles represent Comparative Example 6 in which sludge was not treated by any treatment
- white squares represent Comparative Example 4 in which only hydrogen peroxide was added
- white triangles represent Comparative Example 5 in which sludge was treated with ozone alone
- black circles represent Example 4 in which sludge was treated with ozone in the presence of hydrogen peroxide.
- the decrease in TS concentration in 15 days was approximately 1,300 mg/L for sludge to which only hydrogen peroxide was added and approximately 3,000 mg/L for sludge treated only with ozone.
- the decrease was approximately 9,000 mg/L and the TS concentration was decreased significantly in comparison to the sum of when adding hydrogen peroxide and ozone treatment were conducted independently.
- the amount produced of digester gas from the sludge to which hydrogen peroxide is added and treated with ozone was greater than that from sludge with only hydrogen peroxide or sludge treated with ozone only.
- the yield of digester gas from the sludge to which hydrogen peroxide is added and treated with ozone was greater than the sum of those from sludge with only hydrogen peroxide and sludge treated with ozone only, the combination of hydrogen peroxide and ozone treatment was found to be synergistic.
- the sludge was centrifuged and concentration of phosphorus in the supernatant water was measured. The results are shown in FIG. 6 .
- the concentration of eluted phosphorus was greater than that of ozone treatment alone or adding only hydrogen peroxide and, further, greater than the sum of these.
- the eluted phosphorus in the supernatant water was precipitated as calcium phosphate by adding calcium carbonate solution and then mixing and recovered as solid phosphorus through centrifugal separation. The amount of recovered phosphorus was greatest when the sludge was treated with ozone in the presence of hydrogen peroxide.
- the process of the present invention in which sludge is treated with ozone in the presence of hydrogen peroxide, is highly effective in decreasing, i.e. dissolving, the solids in the sludge, promoting production of digester gas and eluting and recovering the phosphorus in the sludge.
- the hydrogen peroxide is added so that the concentration preferably becomes 20 to 100 mg/L.
- concentration of hydrogen peroxide is lower than 20 mg/L, organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with such low hydrogen peroxide concentration.
- concentration of hydrogen peroxide higher than 100 mg/L is considered uneconomical.
- the ozone injection rate may preferably be 0.01 to 0.10 g-O 3 /g-SS and more preferably 0.03 to 0.07 g-O 3 /g-SS.
- organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with such a small ozone injection rate.
- a larger ozone injection rate enhances both yield of methane and elution of phosphorus, this enhancement becomes slower with an ozone injection rate larger than 0.10 g-O 3 /g-SS. Therefore, an ozone injection rate larger than 0.10 g-O 3 /g-SS is considered uneconomical.
- Excess sludge was taken out from a wastewater treatment plant and treated with ozone while introducing UV radiation.
- the sludge was exposed to an UV lamp having a wavelength of 260 nm and an output of 100 W for 30 minutes.
- the ozone injection rate was 0.05 g-O 3 /g-SS.
- 1.0 L of anaerobically digested sludge having a TS concentration of approximately 25,000 mg/L was introduced into a culture flask having effective volume of 3.0 L.
- the above treated sludge (sludge treated with ozone under UV radiation) was prepared to have a TS concentration of approximately 25,000 mg/L and, then, 1.0 L of the sludge was introduced into the culture flask so that 2.0 L of a mixture having a TS concentration of approximately 25,000 mg/L was obtained.
- the mixture of sludge thus obtained was anaerobically digested at 50° C. (Example 5).
- the wavelength of the UV radiation is preferably 180 to 300 nm
- output of the UV radiation is preferably 5.0 to 200 W and exposure to the UV radiation is preferably 5 to 30 minutes.
- shorter wavelength enhances both yield of methane and elution of phosphorus
- this enhancement becomes slower with the wavelength shorter than 180 nm. Therefore, wavelength shorter than 180 nm is considered uneconomical.
- the wavelength of the UV radiation is longer than 300 nm, organic sludge is not sufficiently denatured and digestion thereof, that is, yield of methane hardly increases.
- phosphorus in the sludge is hardly eluted out with UV radiation of such long wavelength.
- ozone and successive alkali treatments (Example 6), ozone treatment under presence of hydrogen peroxide (Example 7) and ozone treatment under UV radiation (Example 8) were carried out according to the conditions of Examples 1, 4 and 5, respectively.
- the excess sludge was rinsed (Example 9) according to the conditions of Example 3.
- untreated excess sludge was used (Comparative Example 10) instead of the treated excess sludge.
- FIG. 10 The effect of retention time on the TS reduction rate is shown in FIG. 10 .
- white circles represent Comparative Example 10 in which the excess sludge was not treated
- black squares represent Example 6 in which excess sludge was treated with ozone and alkali
- black circles represent Example 7 in which excess sludge was treated with ozone under presence of hydrogen peroxide
- black triangles represent Example 8 in which excess sludge was treated with ozone under UV radiation
- white diamonds represent Example 9 in which excess sludge treated with ozone and alkali was rinsed.
- the amount of eluted phosphorus is greatly increased in addition to solubilization of sludge and transformation into methane.
- the eluted phosphorus is recovered as reusable phosphorus by coagulation and membrane separation and energy and phosphorus are simultaneously recovered from the sludge.
- the amount of eluted phosphorus is greatly increased in addition to solubilization of sludge and transformation into methane.
- the eluted phosphorus is recovered as reusable phosphorus by coagulation and membrane separation and energy and phosphorus are simultaneously recovered from the sludge.
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| CN112876007A (zh) * | 2021-04-22 | 2021-06-01 | 福建沛泰环境工程有限公司 | 一种工业废水处理工艺 |
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| US20050023220A1 (en) * | 2003-08-01 | 2005-02-03 | Barak Phillip W. | Struvite crystallization |
| US7182872B2 (en) * | 2003-08-01 | 2007-02-27 | Wisconsin Alumni Research Foundation | Struvite crystallization |
| US20070000836A1 (en) * | 2005-06-30 | 2007-01-04 | Usfilter Corporation | Process to enhance phosphorus removal for activated sludge wastewater treatment systems |
| WO2007005167A2 (en) * | 2005-06-30 | 2007-01-11 | Siemens Water Technologies Corp. | Process to enhance phosphorus removal for activated sludge wastewater treatment systems |
| WO2007005167A3 (en) * | 2005-06-30 | 2007-03-15 | Siemens Water Tech Corp | Process to enhance phosphorus removal for activated sludge wastewater treatment systems |
| US20070051677A1 (en) * | 2005-09-02 | 2007-03-08 | Siemens Water Technologies Corp. | Screening of inert solids from a low-yield wastewater treatment process |
| US20070209998A1 (en) * | 2006-03-07 | 2007-09-13 | Siemens Water Technologies Corp. | Multivalent Metal Ion Management for Low Sludge Processes |
| US9359238B2 (en) | 2008-03-28 | 2016-06-07 | Evoqua Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US8894855B2 (en) | 2008-03-28 | 2014-11-25 | Evoqua Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US9359239B2 (en) | 2008-03-28 | 2016-06-07 | Evoqua Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US8623213B2 (en) | 2008-03-28 | 2014-01-07 | Siemens Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US8894856B2 (en) | 2008-03-28 | 2014-11-25 | Evoqua Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US8894857B2 (en) | 2008-03-28 | 2014-11-25 | Evoqua Water Technologies Llc | Methods and systems for treating wastewater |
| US8685247B2 (en) | 2009-12-03 | 2014-04-01 | Evoqua Water Technologies Llc | Systems and methods for nutrient removal in biological treatment systems |
| WO2011095805A1 (en) | 2010-02-03 | 2011-08-11 | Cpi Innovation Services Limited | Methods and process plant for the treatment of aqueous organic waste streams |
| US8801931B2 (en) | 2010-02-25 | 2014-08-12 | Evoqua Water Technologies Llc | Hybrid aerobic and anaerobic wastewater and sludge treatment systems and methods |
| US20110220371A1 (en) * | 2010-03-11 | 2011-09-15 | Halliburton Energy Services, Inc. | System and method for fluid treatment |
| US8808544B2 (en) | 2010-08-18 | 2014-08-19 | Evoqua Water Technologies Llc | Contact-stabilization/prime-float hybrid |
| US9359236B2 (en) | 2010-08-18 | 2016-06-07 | Evoqua Water Technologies Llc | Enhanced biosorption of wastewater organics using dissolved air flotation with solids recycle |
| US9783440B2 (en) | 2010-08-18 | 2017-10-10 | Evoqua Water Technologies Llc | Enhanced biosorption of wastewater organics using dissolved air flotation with solids recycle |
| US20120080374A1 (en) * | 2010-10-04 | 2012-04-05 | Pacific Advanced Civil Engineering, Inc. | Ozone and anaerobic biological pretreatment for a desalination process |
| US9038725B2 (en) | 2012-07-10 | 2015-05-26 | Halliburton Energy Services, Inc. | Method and system for servicing a wellbore |
| US10676374B1 (en) | 2012-07-13 | 2020-06-09 | United States Of America As Represented By The Administrator Of Nasa | Ammonia capture and recovery system and method for removing ammonia from a wastewater stream |
| US10131550B2 (en) | 2013-05-06 | 2018-11-20 | Evoqua Water Technologies Llc | Enhanced biosorption of wastewater organics using dissolved air flotation with solids recycle |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4373700B2 (ja) | 2009-11-25 |
| CN1247472C (zh) | 2006-03-29 |
| US20030226803A1 (en) | 2003-12-11 |
| CN1468817A (zh) | 2004-01-21 |
| JP2004058047A (ja) | 2004-02-26 |
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